1. Field of the Invention
The invention relates to an improved fuel injector for internal combustion engines.
2. Description of the Prior Art
DE 101 23 913 A1 has disclosed a fuel injector for internal combustion engines, having a pressure boosting unit for boosting pressure and having a servo-valve for triggering the fuel injector in a pressure-controlled manner. The servo-valve, which is embodied in the form of a 3/2-way control valve, is triggered by and on/off valve embodied in the form of the solenoid valve that executes the pressure control of the fuel injector. The control valve is equipped with a control piston that can move longitudinally in a bore and has a control edge that disconnects a high-pressure system from a low-pressure system. The control piston of the control valve must be provided with various pressure chambers to permit the connection of control lines, the insides of which are subjected to the high pressure of the injection system. This exertion of pressure results in the dilatation of leakage points along high-pressure-tight guides, deformations and dilatations at the control edges of sliding seals, and high notch stresses at bore intersections. These effects due to the exertion of pressure impair the function of the control valve and consequently reduce its fatigue strength.
German patent application 103 37 574.0 has already proposed guiding the control piston in a bush that is externally subjected to system pressure. This significantly reduces dilatations of the high-pressure-tight guides and control edges, deformations of the valve, and high notch stresses at bore intersections. However, it is disadvantageous that the control piston must be ground to fit the bush at two different diameters, which entails high production costs.